Upper respiratory tract secretions: pathophysiology.

Nasal fluid is a heterogeneous substance. It consists largely of a secretory product derived from the 100,000 small seromucous glands. The anterior part of the nose has a relatively high secretory capacity, but this does not seem to be caused by secretion from the 200 anterior serous glands. Compared to sputum, nasal secretion has a lower viscosity, but comparable spinability; it has a lower dry weight, and content of sulphate, sugars and most proteins, but a comparable level of albumin. Watery rhinorrhoea is mainly reflex-mediated. Watery, but not purulent nasal discharge can be reduced by the cholinoceptor antagonist, ipratropium, administered in a dose which matches the degree of the symptoms. It seems likely that the nose, in some respects, can serve as a model for the analysis of airway secretions, but a comparative study of nasal and of bronchial secretions sampled in an identical way is warranted.